Network-based applications that run within web-page browser windows (thin clients) often have inferior user interfaces as compared to native applications that interface directly with the computer operating system (fat clients). In general, native applications have much richer and more responsive user interfaces than do applications that run within browser windows. This is mainly due to limitations that browsers impose on browser-based applications. One of the most significant of these limitations is the lack of a simple and reliable method for communicating between browser windows. To avoid this problem, browser-based applications often operate within the confines of a single window, whereas native applications often provide users with multiple views in multiple windows. As a result, users of browser-based applications often have to navigate between different web pages in order to switch views, which is a time-consuming action.
One method that may be used to provide for communication between browser windows employs JavaScript™ window handles. In this method, when a window B is opened by another window A using a JavaScript command, JavaScript code in both windows A and B can get a handle to the other window and use the handle for direct function calls between the two windows. However, this type of communication is only possible where window B is opened by a JavaScript call or by a HyperText Mark-up Language (HTML) link that is configured to open a new browser window when selected. Thus, if window B is opened from the browser menu, JavaScript cannot be used in either window to get the other window's handle. This type of communication is also limited to communication between browser windows displaying web pages from the same host. Thus, a network-based application having multiple browser windows, each displaying a web page from a different host in the same domain, cannot use this technique to allow its browser windows to communicate with one another.
Another method that may be used to provide for communication between browser windows employs Java™ applets. In this method, multiple instances of a Java applet that reside in different browser windows can communicate with each other using static data members and static methods. Thus, web pages residing in different browser windows that each include an instance of the same Java applet can communicate with each other via inter-applet communication (e.g., Window A JavaScript to Window A applet→Window A applet to Window B applet→Window B applet to Window B JavaScript). However, this method requires that the browser have a Java Virtual Machine (JVM), whereas recent versions of popular browsers do not include a JVM by default.